The present invention relates to electromagnetic methods and apparatus for the treatment of radioactive material-containing volumes and in particular to methods and apparatus for the treatment of radioactive and mixed waste materials for more effective hazardous waste management.
Waste management problems have been exacerbated in the second half of this century by the quantity and toxicity of the waste material generated. Waste quantities have steadily increased due to the population growth and the rapid waste generation rates. In addition, as a result of relatively recent technological innovations, waste materials have become increasingly more toxic. A partial list of hazardous materials which now pose serious environmental and human health hazards include industrial wastes from solvent uses, electrochemical applications, fertilizers, and pesticides, as well as various highly-toxic chlorinated species (for example, polychlorinated dibenzo-p-dioxins, dibenzofurane and biphenyls), and radioactive wastes, many of which were not known in the first half of this century. Soils contaminated with creosote and pentachlorophenol from the operation of wood-treating plants are also a significant environmental hazard. Better technologies are urgently needed to detoxify and isolate these and other hazardous materials from the environment.
The disposal of hazardous materials in near-surface and subsurface formations has become more expensive and difficult as available land and high-quality groundwater resources have diminished. Historical practices, either deliberate or accidental, have left numerous site legacies that must be managed. Although much concern has focussed on species migration and groundwater contaminants, more effective remediation and control may result from soil management and on-site treatment practices. In some instances, modified site operations, as well as chemical and biological treatment technologies have useful roles in waste management. For many contaminated soils, high-temperature incineration is perhaps the most obvious treatment. While appropriate for some liquid wastes, other alternatives should be considered for soil remediation. Low temperature technologies, either chemical or biological treatment, for example, can achieve similar results at somewhat slower rates.
Hazardous radioactive waste materials continue to be an important problem area for the 1990's. These nuclear wastes define a wide range of products generated by a wide range of industrial processes. The waste can result from processes used by hospitals, universities, research institutions, electrical power industry facilities, the Department of Energy, and the Department of Defense. These wastes are not necessarily "esoteric", but comprise such materials as expended ventilation filters, redundant and damaged mechanical equipment such as pumps and valves, contaminated and redundant control equipment, contaminated glassware and containers, protective clothing, ion exchange resins, and sludges.
Attempts to store and dispose of these materials in shallow landfills have, in many cases, resulted in the leakage of radioactive leachates into soils and surface sediments. These primary and secondary wastes do not differ significantly in their physical form from much of the familiar commercial, industrial wastes. They become of special interest only because of their contamination with radioactive nuclides. Radio nuclides themselves cannot be rendered a non-radioactive by any treatment, and can only be made harmless to the environment by stabilization and storage to ensure complete isolation from the biosphere. The duration required to render the radioactive materials safe is dependent on the half-life of decay, and is a function of the toxicity of the radioisotope contaminating the waste. Much of the waste produced from medical diagnostic use and research is contaminated with radioisotopes with short half-lives so that the required decay/storage period is short. Others however, including much of the waste arising from the electrical utility industry and the Department of Defense, are contaminated with radioisotopes of long half-lives and high toxicity and require storage or isolation for very extended periods before they can be considered safe for release to the biosphere.
Stabilization, to prevent mobilization, is a key component to the management of radioactive contaminated waste. Factors to be considered in stabilization include transmutation of chemical compounds containing radioisotopes into forms which are physically more mobile or forms which are more biologically available. An example of this is waste contaminated with tritium, a radioactive form of hydrogen with a half-life of approximately 12.3 years. This isotope is widely used as a marker in organic liquid form for medical, diagnostic purposes and biotechnology research. It is a common contaminant of wastes arising from these industries. During storage of these wastes, it is common to find that biological decay processes within the waste can generate radioactive methane, which is not only an explosion hazard, but is also much more mobile in the environment than the original tritium compounds. Similarly, the conversion through biological decay processes of waste contaminated with radioactive isotopes of lead has resulted in the generation of biologically more mobile organo-lead compounds from wastes originally contaminated with isotopes, only in less biologically available elemental form.
The problems of immobilization are compounded with wastes significantly contaminated, or mixed, with chemicals. First, a wide range of physical and chemical processes can occur which enhance the rates of migration through natural lithology. This includes physical processes, such as increased dissolution rates and decreased precipitation, coprecipitation, or adsorption processes within the natural lithology of the host site. It can also include the formation of compounds of high mobility through chelation processes. This can disrupt the natural stabilization of organic compounds and may act synergistically in conjunction with the radioisotope to increase the risk of exposed organisms, including humans.
These so-called mixed wastes, are subject to substantial regulation under both the Conservation and Recovery Act and the Atomic Energy Act. The practices used to eliminate hazards relating to mixed wastes include either a restriction in the half-lives of the radioactive materials that can be stored or treatment to eliminate the chemical hazards. Many mixed wastes, either because of the long half-lives of some of the radioactive components, or because the chemical wastes are intractable to treatment, cannot conform to this policy. Such wastes are not being identified, or are being stored at the source.
It is therefore an object of this invention to treat radioactive material-containing volumes to manage the waste materials, and, in the case of mixed waste, to separate the radioactive materials from the non-radioactive materials, thus helping to stabilize the waste. A further object of the invention is a method and apparatus for safely containing and controlling the mixed waste materials during the treatment process.